This invention relates to a stainless steel structural member for a blockformer apparatus, to a method for manufacturing such a structural member, and to a blockformer apparatus provided with such a structural member.
A blockformer apparatus has at least one blockformer tower comprising a drainage column having a substantially closed hollow tubular outer jacket which encloses at least one drainage tube placed at least partly within the outer jacket, which drainage tube is conventionally manufactured from stainless steel. In the part of the drainage tube enclosed by the outer jacket, perforations are provided via which whey originating from a curd column present in the drainage tube can be discharged. Present between the drainage tube and the outer jacket is a substantially annular intermediate space, in which a reduced pressure can be created and via which the whey can be further discharged.
In operation, curd particles are supplied at the upper end of the blockformer tower. The curd particles form a curd column in the drainage tube. The curd column rests on a horizontal guillotine blade disposed at the underside of the drainage tube, which guillotine blade is pulled away at regular times. Before the guillotine blade is pulled away, in a lower chamber situated under the drainage column, an elevator platform is moved up to a point just under the guillotine blade. When the guillotine blade has been pulled away, the elevator platform supports the curd column in the drainage tube. The elevator platform is subsequently moved down over a predetermined distance, whereafter the guillotine blade is returned to its initial position again. The guillotine blade thereby cuts off the lower part of the curd column, so that a cheese block is obtained. The cheese block, optionally after being briefly pressed against the guillotine blade with the aid of the elevator platform, is subsequently discharged for further handling, such as, for instance, pressing, weighing, packaging, cuffing into portions, ripening, etc.
It is noted that the drainage tube and the outer jacket can both have, for instance, a rectangular cross section or can both have, for instance, a circular cross section, but that the drainage tube and the outer jacket can also have different cross-sectional shapes.
As appears from the foregoing, the curd column present in the drainage tube moves down through the drainage tube at regular times over a distance equal to the height of the cut-off blocks. During this downward movement of the curd column, the curd particles are progressively compressed and pressed to form a coherent whole under the influence of the curd column""s own weight. In the process, whey is separated, which is discharged via the perforations in the wall of the drainage tube.
From the top down, the curd column therefore become increasingly denser, more solid and drier.
Blockformers have been designed for continuous cheese block production and normally, intermittently, a new amount of curd particles is each time supplied to keep the drainage tube filled to a sufficient extent.
A problem sometimes occurring is that the blocks obtained exhibit cracks. Investigations have shown that such cracks are the result of the static friction arising between the curd column and the inner surface of the wall of the drainage tube. As a result of the static friction, it is possible that a lower section of a curd column already moves down over some distance, while a superjacent section does not yet move down. What also plays a role here is the difference between the static friction coefficient and the dynamic friction coefficient. As a result of the difference in static and dynamic friction coefficient, the so-called stick-slip effect occurs, as a result of which the curd column moves jerkily relative to the wall. As a consequence, the curd column may crack. Depending on the moment at which such cracking or fracture occurs in a curd column, the fracture surfaces can or cannot fuse in a later stage to form an integral entity again.
Comparable problems also occur at other points in a blockformer apparatus where curd parts, or curd blocks or cheese blocks, move relative to a surface of a part of the apparatus. For instance, when a cheese block is being cut off, the guillotine blade moves along curd surfaces both with its top surface and with its bottom surface. When a cheese block is being discharged from the lower chamber, it is moved along side guides and over the elevator platform, so that problems of friction can occur during those operations as well.
An object of the invention is to provide a solution to the problem outlined, or at least to reduce the problem.
To that end, the present invention is directed to a stainless steel structural member for a blockformer apparatus, which structural member has at least one surface along which, in operation, curd slides, wherein at least part of the at least one surface is a micropeened surface having substantially sloping undulations when viewed on a microscopic scale, said surface having been obtained through a micropeening treatment. Also contemplated is a blockformer apparatus incorporating such a structural member.
The present invention is also directed to a method for manufacturing a stainless steel structural member for use in a blockformer apparatus, which structural member has at least one surface along which, in operation, curd move, the method comprising: at least partly finishing the structural member in a conventional manner to obtain a conventional surface roughness; and then subjecting at least part of said at least one surface to a micropeening treatment.